In principle, all animal hair, such as wool, horsehair, angora wool, furs, feathers, and products or textiles produced therefrom, can be used as keratin-containing fibers. However, the invention is preferably used within the scope of heat-assisted hair shaping, in particular straightening of curly human hair and wigs produced therefrom.
A reshaping of keratin-containing fibers is usually carried out in such a way that the fiber is mechanically reshaped and the reshaped form is fixed using appropriate aids. Prior to and/or after this reshaping, the fiber is treated with at least one cosmetic preparation so as to fix the shape that has been newly impressed on the collective fibers.
Within the scope of a permanent wave, for example, keratin-containing fibers are treated with keratin-reducing compounds. After a rinsing process, the fiber is then treated in what is known as the fixation step with an oxidizing agent preparation, rinsed, and freed of the reshaping aids (such as rollers, curlpapers) after or during the fixation step. When a thiol, such as ammonium thioglycolate, is used as the keratin-reducing component, it breaks some of the disulfide bonds of the keratin molecule into —SH groups, whereby the keratin fibers are softened. During the later oxidative fixation, disulfide bonds are again formed in the hair keratin, so that the keratin structure is fixed in the predefined reshaped form.
Within the scope of a temporary styling process, the newly impressed shape of the collective fibers is fixed by applying what are known as hair fixatives. Such hair fixatives are waxes or setting polymers, for example.
When hydrous cosmetics are used, the moist keratin-containing fibers are frequently shaped, the shape is initially mechanically fixed, so as to then remove the water by the application of heat, and additionally bring about fixation of the new shape by the re-formation of the hydrogen bonds within and between the keratin protein strands.
So as to straighten keratin-containing fibers, the curly hair is either wrapped onto rollers having a large diameter of typically more than 15 mm, or the hair is combed straight under the action of a keratin-reducing composition, for example, in a corresponding method.
Instead of using rollers, it is also possible to straighten the fiber on a straightening board. Straightening boards are usually rectangular panels made of plastic material, for example. The fiber is preferably wetted with a liquid. The fibers which are mechanically fixed in the new shape are subjected to a heat treatment as a supporting measure, for example by a hot blower or contact with hot surfaces.
One option of straightening hair is to straighten it with a hot iron. However, the structure of the keratin-containing fiber changes during straightening when heat-treating the hair (see in this regard R. McMullen et al., J. Cosmet. Sci., 1998, 49, 223-244). This change in the fiber structure should be counteracted by appropriate measures or repaired thereafter.